The International Telecommunications Union fosters international cooperation to improve telecommunications of all kinds, coordinates usage of radio and TV frequencies, promotes safety measures and conducts research.
Blas Delgado Ortiz, 24 June 2000

The ITU is the specialized agency of the United Nations which is responsible for
information and communication technologies. ITU coordinates the shared global
use of the radio spectrum, promotes international cooperation in assigning
satellite orbits, works to improve telecommunication infrastructure in the
developing world and establishes worldwide standards. ITU organizes worldwide
and regional exhibitions and forums, bringing together representatives of
government and the telecommunications and ICT industry to exchange ideas,
knowledge and technology. The ITU is active in areas including broadband
Internet, latest-generation wireless technologies, aeronautical and maritime
navigation, radio astronomy, satellite-based meteorology, convergence in
fixed-mobile phone, Internet access, data, voice, TV broadcasting, and
next-generation networks. ITU is based in Geneva, Switzerland.Zoltan Horvath, 27 April 2011

The International Telecommunications Union has a typical flag following the
UNO pattern. The Office of the Secretary General shows a different (I suppose,
modernized)
flag behind Mr Touré: http://www.itu.int/osg/
which is better viewed here (a double-sided flag, apparently), as used at the
World Summit on the Information Society, Tunis 2005:
http://www.itu.int/wsis/plib/detail.asp?y=2005&n=6850 While the office item seems to
have a pale blue globe the outdoor version is more striking. Common are the
white ground, red flash, and dark blue (fimbriated) initials. The above official site has a French version showing an ‘UIT’ logo which ought
to appear on flags as well, I feel. Jan Mertens, 13 April 2007

image located by Jan Mertens, 13 April 2007

Here however we see a dark blue flag with modernized
logo.
Caption: "ITU Flag waving at the [ITU Telecom World, jm] Opening Ceremony, 9
October 1999".
Would there have been three official versions, then?Jan Mertens, 13 April 2007

image located by Esteban Rivera, 22 January 2012

The ITU flag I saw at their main office in Géneve. (Picture taken on November 11, 2011 at their main offices)
I don't know if this picture shows the reverse side or the front side of the
flag (maybe someone can point that out). Also notice that the blue shade in the
flag I attach is actually lighter than we have one featured here. My best guess
is that the ITU flag is the UN light blue background plus the white logo with
the red thunder and the dark blue filled initials with white outline.Esteban Rivera, 22 January 2012

The reverse is flown in the flag . The logo in the centre will be well-known
to anyone who collects stamps, since many countries issued sets in the mid 1960s
to commemorate the organisation's 100th anniversary ( for example -
http://nzpost-stamps.mycdn.co.nz/sites/default/files/issue_historic/1104/1965---ITU22.jpg?1298345582
). Some of these stamps (from Fench-speaking countries) show the initials on the
logo as UIT, so presumably the organisation is at least bilingual, and other
flags with other initials may also exist (it's a shame the French isn't "Union
de Télégraphie Internationale" - if it was then the reverse and obverse would
have both sets of intials!).James Dignan, 22 January 2012